Acute heart failure (AHF) or acute decompensated heart failure (ADHF) encompasses a heterogeneous group of disorders that typically includes dyspnea (shortness of breath), edema (fluid retention) and fatigue. For example, a patient who presents with shortness of breath from an exacerbation of congestive heart failure would fall within the group of AHF patients. However, the diagnosis of AHF can be difficult and the optimal treatment remains poorly defined despite the high prevalence of this condition and its association with major morbidity and mortality. The difficulties surrounding treatment begin with the lack of a clear definition of the disease. The term “acute decompensated heart failure” broadly represents new or worsening symptoms or signs of dyspnea, fatigue or edema that lead to hospital admission or unscheduled medical care. These symptoms are consistent with an underlying worsening of left ventricular function. “Acute heart failure” is sometimes defined as the onset of symptoms or signs of heart failure in a patient with no prior history of heart failure and previously normal function. This is an uncommon cause of AHF, particularly in patients without concomitant acute coronary syndromes. More frequently, AHF occurs in patients with previously established myocardial dysfunction (systolic or diastolic) such as in congestive heart failure (CHF) patients who present with an exacerbation of symptoms or signs after a period of relative stability (Allen and O'Connor, CMAJ 176 (6):797-805, 2007). Consequently, AHF can result without prior history of CHF, be based on a pathophysiological origin in prior CHF patients (functional), or be the result of anatomic causes in prior CHF patients (structural). Thus, AHF can be a functional and/or a structural disease.
The identification of the acute triggers for the decompensation, as well as noninvasive characterization of cardiac filling pressures and cardiac output is central to management. Diuretics, vasodilators, continuous positive airway pressure and inotropes can be used to alleviate symptoms. However, there are no agents currently available for the treatment of AHF that have been shown (in large prospective randomized clinical trials) to provide significant improvements in intermediate-term clinical outcomes.
AHF is the single most costly hospital admission diagnosis according to the Center for Medicare and Medicaid Administration. AHF accounts for more than one million hospitalizations per year and re-hospitalizations within six months are as high as fifty percent. The annual mortality rate approaches fifty percent (for those patients with New York Heart Association class III or IV symptoms). Generally, non-aggressive medical care during the initial hospitalization, sub-optimal treatment before re-admission, and patient noncompliance contribute strongly to the high readmission rate. Fifty percent of patients with classic AHF symptoms before admission receive no alteration in their treatment at the initial consultation with their health care provider (McBride et al., Pharmacotherapy 23 (8):997-1020, 2003).
While AHF was traditionally viewed as a disorder associated with sodium and water retention and left ventricular (LV) dysfunction, it is now also understood to be associated with neurohormonal activation (Schrier et al., The New England Journal of Medicine 341 (8):577-585, 1999). As indicated above, the clinical syndrome of AHF is characterized by the development of dyspnea associated with the rapid accumulation of fluid within the lung's interstitial and alveolar spaces, resulting from acutely elevated cardiac filling pressures (cardiogenic pulmonary edema). More specifically, AHF can also present as elevated left ventricular filling pressures and dyspnea without pulmonary edema. It is most commonly due to left ventricular systolic or diastolic dysfunction, with or without additional cardiac pathology, such as coronary artery disease or valve abnormalities. In addition, a variety of conditions or events can cause cardiogenic pulmonary edema due to an elevated pulmonary capillary wedge pressure in the absence of heart disease, including severe hypertension, particularly renovascular hypertension, and severe renal disease.
Hospital admissions for AHF have increased during the past few decades and are projected to continue to increase in the future. AHF is usually diagnosed and managed based on tradition rather than evidence. In order to reduce the costs associated with this disorder and optimize patient outcomes, new approaches and better treatment options are essential. Diuretic therapy has been the main treatment for symptom relief for pulmonary congestion and fluid retention. Continuous infusions of loop diuretic therapy rather than bolus dosing may enhance efficacy and reduce the extent of diuretic resistance. Catecholamine- and phosphodiesterase-based inotropic therapies are efficacious, but the increased risk of arrhythmogenesis and the potential for negative effects on survival limit their use. NATROCOR (nesiritide marketed by Scios) used in vasodilator therapy, is a pharmacological preload and afterload reducer, but based on clinical trial evidence should be reserved for those with resistance to intravenous nitrate therapy (McBride et al., supra). Vasopressin receptor antagonists and adenosine receptor antagonists offer some improved renal preservation during aggressive diuresis (Tang et al., Current Cardiology Reviews 1 (1):1-5, 2005).
Volume and perfusion status provide useful clues to a patient's cardiac performance and help shape the treatment plan for patients with AHF. Caregivers must frequently reassess the patient's hemodynamic status to determine volume and perfusion status. Volume status is determined by assessing if the patient is wet, dry, or has a balanced fluid level (hypervolemia, hypovolemia, or euvolemia, respectively), and perfusion is assessed by determining if the patient is cold, cool/lukewarm, or warm (has perfusion that is very low, slightly low, or normal, respectively). Evidence of congestion includes the signs of neck vein distension, elevated pressure in the right internal jugular vein, positive abdominal-jugular neck vein reflex, edema, ascites, and crackles (rarely), as well as the symptoms of dyspnea, orthopnea, and paroxysmal nocturnal dyspnea. In addition, various tests can be performed at the time of admission including chest radiographs, arterial blood gas levels, liver function tests, hematologic tests, electrocardiograms, and basic metabolic profile. The findings on physical examination and the results of assays of serum levels of natriuretic peptides can be used to guide treatment in patients with acute decompensated heart failure. Brain natriuretic peptide or B-type natriuretic peptide (BNP) is secreted mainly from the ventricular myocardium in response to elevations in end-diastolic pressure and ventricular volume expansion. The measurement of BNP can aid in diagnosis of CHF as AHF, and BNP levels can also be used to assess clinical status and the effectiveness of therapies during an admission for acute decompensation (Albert et al., Critical Care Nurse 24 (6):14-29, 2004).
While significant advances have been made in the realm of chronic heart failure management, clinicians continue to grapple with optimal strategies to treat acutely decompensated patients including patients afflicted with AHF. There is now an increasing awareness of the complex interplay that occurs between the heart and kidneys among patients with heart failure. As such, many of the traditional therapeutics used to treat this patient population can significantly alter renal function and are, thus, no longer considered optimal treatment options. A more comprehensive approach is desired and the present disclosure addresses this need.